1. Field of the Invention
The present invention relates to a micro column electron beam apparatus, and more particularly, to a micro column electron beam apparatus having a reduced number of interconnections.
2. Description of the Related Art
In general, micro column electron beam apparatuses or micro columns are used for radiating electron beams generated by an electron emission source or a cathode source onto a wafer. Specifically, micro columns are used to form a photoresist pattern on a wafer by supplying electron beams thereon.
Micro columns include an electron emission source or a cathode source, a silicon electrostatic lens or a micro lens, and at least one deflector. The deflectors include 8 bar-shaped electrodes arranged like the blades of a propeller. The deflectors are made of silicon by reactive ion etching (RIE). When a plurality of micro columns with high resolution are used in a lithography process, lithography throughput can be remarkably improved.
However, in conventional micro columns, a plurality of interconnections are needed in one micro column. Specifically, an electron beam deflector as one of the elements of a micro column includes 8 unit electrodes. The unit electrodes include 16 electrodes and are attached to upper and lower portions of the substrate. In order to transmit signals to the electrodes, 16 interconnections are required. In addition, in order to focus electron beams irradiated in a radial shape, a lens module including three silicon lenses is needed at the upper and lower portions of the substrate, and the lens module requires at least 6 interconnections. As such, one micro column has at least 22 interconnections.
Furthermore, when micro columns are arranged in parallel so as to improve productivity, for example, when 4 micro columns are arranged in parallel (2×2), 88 (22×4) interconnections are required. Accordingly, when n×m micro columns are arranged in parallel, 22×m×n interconnections are required. Thus, the number of interconnections increases with the number of micro columns. In addition, since the conventional interconnections are arranged above a substrate, an interaction such as a parasitic capacitance may occur between the interconnections.
A pad electrode to which an external signal is applied is located at an edge of the substrate, and the pad electrode is connected to each electrode of a micro column via the interconnections. In this case, as the pad electrode is formed at the edge of the substrate, the lengths of the interconnections between micro columns close to the pad electrode and micro columns far from the pad electrode may be different from each other although the same signal is applied to the interconnections. As such, the interconnections have different resistances, and due to this resistance difference and the parasitic capacitance, an RC signal delay between the interconnections occurs. As a result, due to the RC signal delay, different signals are applied to an electrode of each micro column to which the same signal should be applied. Thus, a micro column electron beam apparatus having a small number of interconnections and a small signal delay is required.